1. Field of the Invention
The present invention relates to an in-vehicle interior light unit that does not provide heat shield plates, which block the radiant heat emitted from bulbs mounted in bulb cassettes of the in-vehicle interior light unit, directly on the bulb cassettes; that has compact general-purpose bulb cassettes instead of exclusive bulb cassettes; that achieves significantly reduced cost overall by integrally forming the heat shield plates, which block the radiant heat from the bulbs, when pressing a conductive bus bar; and that allows the function of the heat shield plates to be accomplished at low cost.
2. Background Art
As illustrated in FIG. 7, a conventional in-vehicle interior light unit is constituted of a base 50, which is a non-heat-resistant resin housing, a bus bar 10 formed of a metal member, which is a conductive member, and mounted on the base 50, heat-resistant resin bulb cassettes 30 to be mounted respectively at right and left of the bus bar 10, and horizontal mount type lighting boat-shaped bulbs 40 to be mounted in the bulb cassettes 30. FIG. 7 is an exploded perspective view of the conventional in-vehicle interior light unit from which the base 50 has been removed. The bus bar 10 is formed by punching an electrically conductive metal material. The bulb cassettes 30 are formed of a heat-resistant resin. Heat shield plates 20 having a heat shielding function are formed integrally with the bulb cassettes 30 made of a heat-resistant resin, the heat shield plates 20 being formed by using the same heat-resistant resin as that of the bulb cassettes 30. The heat-resistant resin bulb cassettes 30 to be respectively mounted at right and left of the bus bar 10 are set at the right and left positions within the extension of the bus bar 10 such that the heat shield plates 20 at right and left oppose each other. The boat-shaped bulbs 40, which are used in a horizontally rested state, are mounted in the right and left bulb cassettes 30 placed on the base 50.
The radiant heat emitted as illumination light from the boat-shaped bulbs 40 is blocked by the heat shield plates 20, which are horizontally long and which are made of a heat-resistant resin.
However, the aforesaid conventional bulb cassettes 30 made of a heat-resistant resin use the boat-shaped bulbs 40 adapted to be horizontally mounted, thus requiring a horizontally large area and space overall. Further, the conventional bulb cassettes 30 have been posing drawbacks in that the bulb cassettes 30 themselves must be formed of a heat-resistant resin, which inevitably requires high material cost and time for molding, and the bulb cassettes 30 themselves require a horizontally large installation space, meaning that the area for installation on the conventional base 50 is undesirably large. In addition, the bulb cassettes 30 have been handled as exclusive components, disadvantageously lacking in versatility.
As a heat shielding structure of a conventional in-vehicle interior light, an invention has been disclosed in which a heat shielding structure includes a base formed of a resin material having low heat resistance, such as polypropylene, and a wall surface located adjacently to the bulb incorporated in the base, a bulb cassette for installing the bulb in the base is formed of a heat-resistant resin, and a heat shield wall interposed between the bulb and the wall surface is connected to the bulb cassette (refer to Patent Document 1).
[Patent Document 1] Japanese Patent Application Laid-Open No. 2007-30767